The first line binds an unbound key to the function. The second line binds a key already bound in org-mode to the function. The remaining lines define the hook.

I start Emacs anew and describe the keys. C-c C-x C-SPC is bound to my-function and C-c C-x C-z is bound to the default org-resolve-clocks in an org buffer and to my-function elsewhere. If I run the binding code interactively in an org buffer with M-::